A hamburger, or simply a burger, is a dish consisting of fillings—usually a patty of ground meat, typically beef—placed inside a sliced bun or bread roll. The patties are often served with cheese, lettuce, tomato, onion, pickles, bacon or chilis with condiments such as ketchup, mustard, mayonnaise, relish or a "special sauce", often a variation of Thousand Island dressing and are frequently placed on sesame seed buns. A hamburger patty topped with cheese is called a cheeseburger.